1. Field of the Invention
This invention relates to a recording medium suitable for use in recording methods using an ink, particularly a recording medium excellent in ink receptibility and distinctness of recorded image, as well as to a recording method utilizing said recording medium.
2. Description of the Prior Art
In ink jet recording, a recording liquid is discharged and converted to propelled droplets by various discharging methods such as (a) an electrostatic attraction method, (b) a method wherein a recording liquid receives mechanical vibration or displacement by a piezoelectric element and (c) a method wherein a recording liquid is heated to foam and the resulting pressure is utilized, whereby the part or whole of the propelled droplets are allowed to deposit onto a recording medium such as paper or the like. This ink jet recording is drawing public attention as a recording method which generates less noise and permits high speed and multi-color printing.
As the ink for ink jet recording, there are mainly used aqueous inks which meet the requirements for safety and recording characteristics, and these inks contain, in many cases, a polyhydric alcohol or the like for prevention of nozzle plugging and enhancement of discharging stability.
As the recording medium for ink jet recording, there have conventionally been used ordinary papers and so-called ink jet recording papers constituted of a substrate and a porous ink-receiving layer formed on the substrate. However, with the improvements of performance of ink jet recording equipment such as faster recording, multi-color recording and the like as well as with the spread of such equipment, superior and more flexible characteristics are being required for recording media. That is, a recording medium for ink jet recording capable of providing a recorded image of high resolution and high quality must satisfy basic requirements such as shown below.
(1) The reception of an ink by the recording medium is as quick as possible.
(2) When two ink dots overlap, the dot formed later does not penetrate into the dot formed previously.
(3) Ink dots spread on the recording medium within the range of the maximum acceptable diameter.
(4) The shape of ink dots formed on the recording medium is close to a true circle and the circumference of the circle is smooth.
(5) The ink dots formed on the recording medium have a high optical density and their circumferences are not blurred.
In order to obtain a recorded image quality comparable to that in color photography, by multi-color ink jet recording, the recording medium must further satisfy, such requirements as mentioned below in addition to the above basic requirements.
(6) The coloring components of ink can develop excellent colors on a recording medium.
(7) Since the ink droplets which number as many as the number of possible ink colors may possibly be deposited at the same spot, the recording medium is excellent particularly in ink fixing.
(8) The recording medium has a high degree of whiteness.
No recording medium is known yet which satisfies all the above requirements.
In many of conventional recording media for image formation consituted of a substrate and a porous ink-receiving layer formed on the substrate, a recording liquid is received by the pores of the ink-receiving layer and is fixed. Consequently, the recording liquid penetrates deep into the ink-receiving layer resulting in low distinction of recorded image.
Meanwhile, in conventional recording media constituted of a substrate and a non-porous ink-receiving layer formed on the substrate, a non-volatile component in ink such as a polyhydric alcohol remains on the recording media for a long time. (That is, the drying and fixing of ink takes long time.) This causes, when the recorded image is touched, staining of clothes or impairment of recorded image.